IMAGE  EVALUATION 
TEST  TARGET  (MT-3) 


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Hiotographic 

Sciences 
Corporation 


23  WfST  MAIN  STRIET 

WIBSTM.N.Y.  MSUd 

(716;S72-4S03 


'^ 


,> 


Us 


CIHM/ICMH 

Microfiche 

Series. 


CiHIVi/ICIViH 
Collection  de 
microfiches. 


Canadian  Institute  for  Historical  Microreproductions  /  Institut  Canadian  de  microreproductions  historiques 


ihhhA 


Tachnicai  and  Bibliographic  Notaa/Notaa  tachniquaa  at  bibliographiquaa 


Tha  Inatituta  haa  anamptad  to  obtain  tha  baat 
original  copy  availabia  for  filming.  Faaturaa  of  thia 
copy  wliicti  may  ba  bibliographieally  uniqua. 
which  may  altar  any  of  tha  imagaa  in  tha 
raproduction.  or  which  may  significantly  changa 
tha  uaual  mathod  of  filming,  ara  ehackad  balow. 


HColourad  covara/ 
Couvartura  da  coulaur 


rn   Covafa  damagad/ 


D 


D 


EZ] 
D 


a 


Couvartura  andommag^ 


Covara  raatorad  and/or  laminatad/ 
Couvartura  raataurAa  at/ou  paiiiculAa 


r~~1    Covar  titia  miaaing/ 


La  titra  da  couvartura  manqua 


□   Colourad  mapa/ 
Cartaa  giographiquaa  mn  coulaur 


Colourad  ink  (i.a.  othar  than  blua  or  black)/ 
Encra  da  coulaur  (i.a.  autra  qua  blaua  ou  noira) 


I — I   Colourad  plataa  and/or  iiluatrationa/ 


D 


Planchaa  at/ou  iiluatrationa  an  coulaur 


Bound  with  othar  matarial/ 
Ralii  avac  d'autraa  documanta 


Tight  binding  may  cauaa  shadowa  or  diatortion 
along  intarior  margin/ 

La  rB  liura  sarria  paut  cauaar  da  I'ombra  ou  da  la 
diatorsion  la  long  da  la  marga  intAriaura 

Blank  laavas  addad  during  rastoration  may 
appaar  within  tha  taxt.  Whanavar  possibia,  thasa 
hava  baan  omittad  from  filming/ 
II  aa  paut  qua  cartainaa  pagas  blanchas  ajoutias 
lora  d'una  raatauration  apparaiaaant  dana  la  taxta, 
mais,  toraqua  cala  Atait  posaibia,  caa  pagaa  n'ont 
paa  «t«  film^aa. 

Additional  commanta:/ 
Commantairaa  supplAmantairaa; 


L'Inatitut  a  microfilm*  la  maillaur  axamplaira 
qu'il  lui  a  iti  posaibia  da  sa  procurar.  Las  details 
da  cat  axamplaira  qui  sont  paut-Atra  uniquas  du 
point  da  vua  bibliographiqua.  qui  pauvant  modifiar 
una  imaga  raproduita.  ou  qui  pauvant  axigar  una 
modification  dana  la  mithoda  normala  da  filmaga 
sont  indiquia  ci-daaaoua. 


rn   Colourad  pagaa/ 


n 


Pagaa  da  coulaur 

Pagaa  damagad/ 
Pagaa  andommagiaa 

Pagaa  raatorad  and/oi 

Pagaa  raataurAas  at/ou  palliculias 

Pagaa  discolourad.  stainad  or  foxa< 
Pagaa  dicolortes.  tachattes  ou  piques 

Pagaa  datacnad/ 
Pagaa  ditachtos 

Showthrough/ 
Tranaparanca 

Quality  of  prin 

Quality  inigala  da  I'imprassion 

Includaa  supplamantary  matarii 
Comprand  du  matirial  supplimantaira 

Only  adition  availabia/ 
Saula  Mition  disponibia 


pn  Pagaa  damagad/ 

pn  Pagaa  raatorad  and/or  laminatad/ 

r~7]  Pagaa  discolourad.  stainad  or  foxad/ 

r~n  Pagaa  datacnad/ 

r~7  Showthrough/ 

|~n  Quality  of  print  variaa/ 

rn  Includaa  supplamantary  matarial/ 

I — I  Only  adition  availabia/ 


Pagaa  wholly  or  partially  obscured  by  errata 
slips,  tissuaa.  etc..  hava  baan  rafilmed  to 
ensure  the  best  possible  image/ 
Lea  pages  totalement  ou  partieilement 
obscurcies  par  un  fauillet  d'errata.  una  pelure. 
etc.,  ont  itt  filmies  k  nouveau  da  faqon  d 
obtanir  la  mailleure  image  possible. 


This  item  is  filmed  at  tha  reduction  ratio  checked  below/ 

Ce  document  eat  film*  au  raux  da  rMuction  indiqu*  ci-deaaoua. 

10X  14X  18X  22X 


26X 


30X 


y 


12X 


lex 


aox 


24X 


28X 


32X 


Th«  copy  fiimMl  h«r«  has  lM«n  r«produc«d  thanks 
to  ths  gsnsrosity  of: 

New  Brunswick  MuMum 
Saint  John 


L'sxamplairs  filmi  fut  rsproduit  grl^ea  i  la 
fljinirosit*  da: 

Now  Brunswick  IMuscum 
Saint  John 


Tha  imagas  appaaring  hara  ara  tha  bast  quality 
possibia  eonsidaring  tha  condition  and  lagibillty 
of  tha  original  copy  and  in  kaaping  with  tha 
filming  contract  spacificationa. 


Laa  imagaa  suhrantaa  ont  4ti  raproduitas  avac  la 
plua  grand  soin,  eompta  tanu  da  la  condition  at 
da  la  nattatA  da  raxamplaira  filmA.  at  •» 
conformity  avac  laa  condltiona  du  eontrat  da 
filmaga. 


Original  copiaa  in  printad  papar  eovars  ara  filmad 
baginning  with  tha  front  covar  and  anding  on 
tha  last  paga  with  a  printad  or  illuatratad  impraa- 
sion,  or  tha  back  covar  whan  appropriata.  All 
othar  original  copiaa  ara  filmad  baginning  on  tha 
first  paga  with  a  printad  or  illuatratad  impraa- 
sion,  and  anding  on  tha  laat  paga  with  a  printad 
or  iliustrstad  imprassion. 


Laa  axampiairaa  originaux  dont  la  couvartura  an 
papiar  aat  imprimte  sont  fiimis  an  commandant 
par  la  pramlar  plat  at  an  tarminant  soit  par  la 
damiira  paga  qui  comporta  una  amprainta 
d'Impraasion  ou  d'illustration,  soit  par  la  sacond 
plat,  salon  la  cas.  Tous  las  autras  axampiairaa 
originaux  sont  filmto  an  commandant  par  la 
pramlAra  paga  qui  comporta  una  amprainta 
dlmpraaaion  ou  d'illuatration  at  •n  tarminant  par 
la  darniAra  paga  qui  comporta  una  talla 
amprainta. 


Tha  laat  racordad  frama  on  aach  microficha 
shall  contain  tha  symbol  —^(moaning  "CON- 
TINUED"), or  tha  symbol  y  (moaning  "END"), 
whichavar  appiiaa. 


Un  daa  symbolaa  suivants  apparaftra  sur  la 
darniAra  imaga  da  chaqua  microficha.  salon  la 
caa:  la  symbols  — »•  signifia  "A  SUiVRE".  la 
symbols  ▼  signifia  "FIN". 


Mapa.  plataa.  cliarts.  ste..  may  ba  filmad  at 
diffarant  raduction  ratioa.  Thoaa  too  larga  to  ba 
antiraly  includad  In  ona  axpoaura  ara  filmad 
baginning  in  tha  uppar  laft  hand  comar,  laft  to 
right  and  top  to  bottom,  aa  many  framaa  aa 
raquirad.  Tha  following  diagrama  illustrata  tha 
mathod: 


Laa  cartaa.  planchaa.  tabiaaux.  ate.  pauvant  Atra 
filmte  A  daa  taux  da  reduction  diffirants. 
Loraqua  la  documant  ast  trop  grand  pour  Atra 
raproduit  an  un  saul  clichA.  il  ast  filmA  k  partir 
da  I'angia  aupAriaur  gaucha.  da  gaucha  k  droita. 
at  da  haut  an  bas.  an  pranant  la  nombra 
d'imagas  nAcassaira.  Las  diagrammas  suivants 
illustrant  la  mAthoda. 


1  2  3 


1 

2 

3 

4 

5 

6 

'  ii 


I  " 


'    Hi' 


I  !' 


I  i, 


III 


1 


VOLUME  XX\ 


BOT 


UPON  POL 


Many  cas 
widely  separa 
in  i860,  rec 
thirteen  gene 
Strasburger  w 
logical  basis, 
tions  have  be 
notably  Dode 
frey  (1895), 
works,  in  so  f 
marized  belov 
bryony  hithe 
which  Engelr 
figured  {p/.  2^ 
case  was  cite 
suggests  that 
in  Opittiiia  gin 
hence  polyene 
explained  as 
this  family,  I 
embryonic,  at 


VOLUME  XXV 


NUMBER  4 


Botanical   Gazette 


APRIL   1898       ^6%^^.X,f&ff,CSt^, 


upon  polyembryony  and  its  morphology 

opuntia  vulgaris. 

\V.  F.  G  A  N  O  N  (i. 


in 


kmyLtJ^ 


(with    plate    XVI ) 

Many  cases  of  polyembryony  are  now  known,  occurring  in 
widely  separated  groups,  Braun,  in  his  summary  of  the  subject 
in  i860,  recorded  twenty-one  cases  in  twelve  families  and 
thirteen  genera,  which  number  has  been  added  to  by  others. 
Strasburger  was  the  first  to  thoroughly  investigate  its  morpho- 
logical basis,  and  since  his  paper  in  1878  important  contribu- 
tions have  been  made  to  the  subject  by  several  investigators, 
notably  Dodel  (1890),  Overton  (  189 1 ),  Tretjakow  (1895) ,  Jef- 
frey (1895),  ^^^  Hegelmaier  (1897).  The  results  of  these 
works,  in  so  far  as  they  touch  this  subject,  will  be  found  sum- 
marized below.  In  the  Cactaceae,  the  only  case  of  polyem- 
bryony hitherto  known  has  been  that  of  Opuntia  tortispitta, 
which  Engelmann,  in  his  Cactace.t  of  Whipple's  expedition 
figured  (//.  2j,fig.4^  as  having  two  embryos  in  one  seed.  This 
case  was  cited  by  Braun  (p.  155,  //.  5,  figs.  18-20),  who  also 
suggests  that  the  four  cotyledons  which  he  had  himself  noticed 
in  Opuntia  glaucophylla  may  indicate  a  fusion  of  two  embryos  and 
hence  polyembryony,  though  he  points  out  that  it  may  also  be 
explained  as  fasciation.  While  studying  the  seedling  stages  in 
this  family,  I  have  found  that  Opuntia  vulgaris  is  markedly  poly- 
embryonic,  and  I  may  here  add  that  although  I  have  worked 


221 


222 


BOTANICAL  GAZETTE 


[aI'RII. 


over  the  seedlings  of  some  seventy-five  species  in  this  family  I 
have  seen  no  other  case  of  it. 

The  plants  from  which  my  seeds  were  taken  have  been  grow- 
ing and  flowering  luxuriantly  for  at  least  four  years  in  the 
Botanic  Garden  of  Smith  College.  They  agree  with  the  char- 
acters given  in  books  for  that  species,  but  the  source  from  which 
they  came  into  the  garden  is  unknown.  They  set  seed  every 
year  in  great  abundance.  When  the  seeds  are  planted,  from 
many,  perhaps  a  half,  of  them  more  than  one  seedling  comes  up, 
and  there  is  the  greatest  variation  in  the  number,  size,  and 
degrees  of  union  with  one  another  of  these  seedlings.  This 
variety  is  best  made  evident  by  the  figs,  i  to  5,  typical  cases 
drawn  the  natural  size,  and  of  course  there  are  all  stages 
between.  I  have  not  tried  to  follow  them  further,  but  what  1 
have  noticed  seems  to  show  that  the  larger  of  a  set  crowds  out 
the  others.  It  is  now  important  to  ascertain  the  morphological 
origin  of  this  polyembryony. 

The  ovule  of  Opuntia  vulgaris  is  at  first  amphitrcpous,  but 
in  its  development  it  becomes  elongated  and  bent,  at  the  same 
time  turning  around  in  such  a  way  that  the  funiculus  makes 
a  complete  turn  around  it,  so  that  finally  it  simulates  a  cam- 
pylotropous  condition  {fig.  6).  Its  development  in  other  spe- 
cies of  this  genus,  together  with  the  development  of  other 
species  of  other  genera  in  this  family,  has  been  described  by 
d'Hubert,  and  his  account  fits  this  species  fairly  well.  Inside  of 
the  funiculus  are  the  integuments,  made  up  of  three  distinct 
layers  of  cells,  and  inside  of  these  is  a  nucellus,  which  becomes 
absorbed,  except  for  a  small  portion  (at  x,fig.  6),  by  the  embryo 
as  the  seed  ripens.  Finally  there  is  the  distinct  embryo  sac,  in 
which  there  forms  after  fertilization  an  abundant  endosperm, 
which  consists  of  protoplasts  without  cellulose  walls,  the  whole 
of  course  absorbed  by  the  growing  embryo. 

In  ripe  seeds  one  finds  usually  a  large  embryo  nearly  filling 
it,  with  others  much  smaller  and  pressed  to  one  side.  In  half- 
ripe  seeds  one  finds  such  a  condition  as  is  shown  in  fig.  8,  where 
there  is  one  larger  embryo  with  several  smaller  ones,  and  usually 


1898.1 


POLYEMBRYON.Y  AND  ITS  MORPHOLOGY 


223 


the  larger  comes  not  from  the  microj)ylar  extremity  of  the 
embryo  sac,  but  from  some  point  on  its  wall  a  little  removed. 
In  other  cases  one  sees  a  single  embryo  springing  from  the 
micropylar  end  and  one  or  more  from  the  walls,  as  '\vi  fig.  7.  Or 
again,  though  rarely,  there  is  a  single  embryo  at  the  micropylar 
end,  as  in  fig.  g.  There  is  a  close  resemblance  between  these 
figures  and  those  given  by  Strasburger  for  Citrjis  Aurantium 
{fig.  jy).  If  now  these  be  examined  in  a  still  younger  stage,  it 
becomes  clear  thcit  the  embryos  come  from  two  different  posi- 
tions :  first,  from  a  rather  irregular  mass  of  tissue  which  lies  at 
the  micropylar  end  of  the  embryo  sac,  and  extends  thence  along 
its  wall ;  and  second,  directly  from  the  wall  itself.  Both  of 
these  conditions  are  well  shown  in  fig.  10.  It  is  imjjortant  to 
notice,  however,  that  some  cases  seeming  to  belong  to  the  latter 
category  belong  really  to  the  former,  as  is  illustrated  hy  fig.  1$, 
where  the  wall-standing  embryos  are  shown  to  spring  really 
from  the  mass  at  the  micropylar  end,  but  this  is  not  the  case 
with  all  of  the  wall-standing  embryos,  for  sections  show  that  in 
many  cases,  i.  c^  fig.  10,  these  are  entirely  independent  of  that 
mass.  It  is  probable  that  the  irregular  embryos  come  as  a  rule 
from  the  micropylar  mass,  while  the  regular  ones  are  from  the 
walls,  for  all  I  have  seen  in  that  position  have  regularly  two 
cotyledons. 

So  far,  in  tracing  backwards  the  origin  of  the  polyembryony, 
everything  is  plain,  and  it  is  easy  to  find  plenty  of  cases  such  as 
are  here  figured.  At  this  stage,  the  entire  distinctness  of  the 
micropylar  mass  from  the  nucellus  beneath  {sec  figs.  10  and  //) 
and  its  close  resemblance  to  that  described  and  figured  by  Jef- 
frey which  he  traced  to  its  origin  in  a  fertilized  egg  cell,  would 
lead  one  to  suppose  that  we  have  here  a  similar  case  ;  while  in 
the  wall-standing  embryos,  which  are  so  sharply  distinct  from  the 
nucellus  {fig.  11)  that  an  origin  from  nucellus  seems  excluded, 
only  an  origin  from  an  endosperm  cell  would  appear  possi- 
ble, a  condition  which  is  yet  unknown.'  But  the  earlier  stages 
show  that  both  of  these  suppositions  are  incorrect.     In  a  great 

'  This  was  my  own  opinion  in  both  cases  at  the  time  this  paper  was  read  before  tiii; 


324 


BOTANICAL  GAZETTE 


[aI'KII. 


abundance  of  material  which  shows  the  ovules  in  all  stages 
before  and  at  the  time  of  fertilization,  and  also  all  staji^es  after 
that  represented  in  fig,  to,  I  was  able  to  find,  after  prolonged 
and  careful  search,  only  three  cases  which  show  the  origin  of 
the  embryos,  but  happily  they  leave  no  doubt  on  the  subject.  I 
think  this  stage  must  be  passed  through  very  rapidly,  and  per- 
haps at  night,  when  none  of  my  material  was  collected. 

In  stages  earlier  than  fig.  lo,  the  pollen  tube  can  usually  be 
seen  in  the  micropylar  region  of  the  nucellus,  but  an  egg  cell 
cannot  be  detected.  Instead  there  regularly  lies  in  its  position 
a  crumpled  mass  of  protoplasm  {fig.  12,  14,  pr.),  shrunken  in 
my  material  by  the  weak  alcohol  used  to  preserve  it.  I  think 
the  egg  cell  disappears  early  in  the  development  of  the  ovule,  a 
point  which  will  be  cleared  up  by  a  complete  study  of  the  devel- 
opment of  the  embryo  sac,  now  being  made  by  one  of  my 
students.  At  all  events  there  is  certainly  no  egg  cell  present  in 
any  of  my  preparations  at  the  period  when  the  embryo  building 
begins.  The  nucellus  cells  near  the  pollen  tube  arc  rich  in  con- 
tents, and  in  one  case  {fig.  12)  I  have  found  these  beginning 
to  bud  out  into  the  embryo  sac.  That  these  represent  the  begin- 
ning of  the  formation  of  the  micropylar  mass,  I  think  there  can 
be  no  question.  It  is  precisely  in  this  way  that  the  adventi- 
tious embryos  originate  in  P'unkia  and  other  cases,  as  described 
so  fully  and  clearly  by  Strasburger.  In  another  case  {fig.  /?) 
there  are  present  not  only  the  richly  protoplasmic  nucellus  cells 
near  the  pollen  tube,  here,  however,  not  budding,  but  also  other 
nucellus  cells  a  little  removed  and  separated  by  a  space  filled 
with  cells  rather  poor  in  contents;  and  these  cells  with  rich  con- 
tents are  also  distinctly  budding  out  {fig.  /?,  x).  Now  these,  I 
believe  there  can  be  no  doubt,  are  the  beginning  of  the  wall- 
standing  embryos  ;  it  is  quite  probable  that  at  first  they  are  con- 
tinuous with  those  near  the  pollen  tube,  but  are  removed  from 
them  by  the  growth  in  length  of  the  embryo  sac,  which  at  this 
time  is  very  rapid.     At  all  events  they  are  nucellus  cells.     The 


Society  for  Plant  Morphology  and  Physiology,  Dec.  29,  1897.     1  had  not  then  found 
the  three  cases  next  to  be  desciibed,  which  prove  the  origin  to  be  different. 


1898] 


POl.VEMfiRYOiVY  AND  ITS  MORPHOLOGY 


til 


third  case  I  have  found  is  represented  in  fig.  /./,  which  is 
more  advanced  thany?^.  /j,  and  where  the  differentiation  of  the 
richly  protoplasmic  cells  of  the  embryonic  mass  from  the  nearly 
empty  cells  beneath  it  is  fairly  sharp,  but  nevertheless  the  rela- 
tions of  the  two  kinds  are  still  sufficiently  close  to  show  the 
origin  of  the  one  from  the  other.  Another  section  of  the  same 
specimen  shows  a  similar  connection  of  the  other  mass  of 
embryonic  tissue  with  the  nucellus. 

From  these  cases  it  is  clear  that  in  this  species  the  embryos 
of  both  positions  arise  from  the  nucellus,  and  in  this  respect  agree 
with  Funkia.Nothoscordum,  Citrus,  and  others,  the  usual  method. 

A  synopsis  of  the  modes  of  origin  of  polyembryony  is 
given  by  Tretjakow,  which  in  synopsis,  with  the  additions  made 
by  others,  and  excluding  cases  due  to  branching  of  the  nucellus, 
union  of  two  ovules,  presence  of  two  or  more  embryo  sacs  in 
one  nucellus,  etc.,  are  as  follows :  From  cells  of  nucellus  near 
the  micropyle,  Ftinkia  and  others  (Strasburger) ;  from  a  second 
egg  cell,  Santalum,  or  from  its  doubling  Sinningin  (Strasburgcr)  ; 
from  sy  nergids.  Mimosa  Denhartii  ( Guignard) ,  Iris  Sibirica  ( Dodel ) , 
and  perhaps  in  Lilitim  Martagon  (Overton)  ;  from  the  antipodals 
and  synergids.  Allium  odortim  (Tretjakow) ;  from  the  branching 
of  a  mass  of  tissue  derived  from  the  fertilized  egg  cell  (Jeffrey)  ; 
finally,  Hegelmaier  points  out  the  occurrence  in  Allium  odorum 
of  embryos  from  e.^'g  cell,  synergids,  antipodals  and  nucellus 
cells,  all  in  the  same  species  and  individuals.  There  still  remain 
as  possible  origins,  endosperm  and  integument.  In  all  known 
cases,  except  Ccelebogyne,  the  production  of  the  new  embryos 
takes  place  only  after  fertilization,  or  at  all  events  after  the 
entrance  of  the  pollen  tube. 

A  question  of  great  interest  now  arises  as  to  the  significance 
of  polyembryony.  Strasburger,  though  he  mentions  that  it 
recalls  apogamy,  then  recently  discovered  by  Farlow,  contents 
himself  with  referring  to  the  extra  embryos  as  "  Adventivknos- 
pen"  or  "vegetative  Adventivkeime."  Pfeffer''  has  suggested 
that  it  is  but  a  case  of  budding,  and  that  the  specific  conditions 

'  Pflanzenphysiologie  i  :  29.  1897. 


aa6 


HO  TANICAl.  GA/.E  TTE 


Iaprii. 


in  the  embryo  sac  determining  the  form  of  the  sexually  pro- 
duced embryo,  jj[ive  the  same  form  to  the  adventitious  embryos. 
Tretjakow  suggests  that  the  development  from  the  antipodals 
represents  a|)ogamy,  the  anti|)odals  being  homologous  with  the 
vegetative  cells  of  the  prothallus,  but  this  explanation  will  not 
a[)ply  to  the  origin  from  nucellus  cells.  Jeffrey  has  nothing  to 
say  on  this  point,  while  Ilegelmaier  concludes  his  paper  thus: 

Die  vcrlialtiiissiniUsi^e  Scltenhcit  dcr  deni  Kinpparat  cntspriiiK'ciuicn 
I'olycnibrvoiiie  hci  //.  ottonim  ciiierseits  uiid  das  oftere  ^elc^cntlichu  Vor- 
koininen  dicscr  Form  l)ei  vcrschiedciicn  andereii  IMIaii/cn  aiidercrseits  koiintc 
viflleiclu  y.ii  dcr  AufTasstin^  flUiren,  class  ihr  V^)rkniiiiiieti  bei  unsercr  I'tlan/e 
Uhcrhatipt  nicht  in  dieselbe  Kcihc  niit  dem  V'orkoiiiinen  dcr  andercti  Koriiicn 
von  Folycnil)ryonic  bei  ihr  zu  stellcn  iind  ihr  /iissannncntrcffcn  mit  diescn  and- 
crcn  Korincn  mchr  nur  ein  /ufiiiliges  sei.  Aber  mindcstcns  fUr  diesc  Ictzti-rcn 
ist  doch  wohl  die  Annahnie  iinahweisbar,  das  irgcndwelchc  gemcinschaftlichcn 
Ursachen  vorhandcn  sein  miisscn,  flir  dercn  Krkenntniss  durch  ein  Spiel  mit 
niorphologischen  Honiologien  nichts  zu  gewinncn  sein  wllrde. 

In  general  for  a  new  feature  one  of  three  origins  may  be 
supposed.  First,  it  may  be  some  incidental  growth  or  functional 
condition.  Mere  comes  the  explanation  of  budding,  and  Pfef- 
fer's  explanation  of  the  assumption  of  the  embryo  form  through 
specific  (jualitics  of  the  embryo  sac.  But  polyembryony  seems 
too  distinct  and  elaborate  a  process  to  be  thus  explained.  Sec- 
ond, it  may  be  a  relic  of  some  older  condition  now  disappear- 
ing. Hut  its  very  different  morphological  origins  arc  against 
this.  Here  comes  its  explanation  as  apogamy,  but  this  does  not 
explain  the  origin  from  the  nucellus.  Third,  it  may  be  the  early 
stages  in  the  development  of  something  new.  It  can  hardly 
yet  be  of  any  service  to  the  plants,  for  many  of  the  embryos  are 
absorbed  before  the  seeds  are  ripe,  and  in  other  cases  usually 
but  one  develops,  though  perhaps  one  of  the  smaller  may  some- 
times take  the  place  of  the  leader  if  this  is  destroyed.  Its  origin 
in  several  distinct  groups  and  by  several  distinct  methods  seems 
to  imply  that  there  is  some  virtue  in  the  development  of  the 
extra  embryos,  and  that  their  appearance  is  controlled  by  that 
influence,  whatever  it  may  be,  which  is  much  more  powerful 
than  mere  morphological  inertia,  and  which  elsewhere  forms  new 


I8q8] 


roi.YI.MHKYONY  ANH  ITS  MOKniOl.OCY 


327 


Structures  from  the  most  different  morphological  origins.  In  its 
independent  appearance  in  distinct  group}"  it  is  comparable  with 
the  appearance  of  heterospory,  but  whether  polyembryony  like 
heterospory  will  lead  to  some  higher  condition  remains  lo  be 
seen,  though  we  shall  not  see  it. 

6.MITH    CoilKCK,    NORIMAMI'TON,    MASS. 

BIMLIOC.RAl'HY. 

Hkaun,  a. —  Ucber  I'olycnibryonie  und  Keiimin><  von  Cu-'lcboKyne.   i860 

IIkcki.maikk,  F. —  Zur  Kenntnissilur  I'olyenibryonie  \v>\\  Allium  oilorum 
L.     Hot.  Zeit.  55  :   133.  i8y7. 

IIuiu:kt,  K.  I)'.-  -  Rechercbt's  siir  Ic  sue  cnibryoniiaire  <lts  |)l;m'.ts  grasses. 
Ann.  Sci.  Nat.  VIII.  a  :  37.  i8y6. 

Jkkkkicy,  K.  C. —  I'olyeinbryony  in  Erytbroniuni  u  icricanuin.  Ann. 
Mot.  9;  537.  1891;. 

Stkasmi  k  ,1  ,  K. —  Ueber  Polyombryonie.  Zeilscbr.  f.  X;nui\v,  la  ;  647. 
1878. 

i  UKTJAKOW,  S. —  Die  Hetbciligung  «U'r  Antipoden  in  Fiillen  der  I'oly- 
embryonie  bei  Allium  odorum  L.    Her.  d.  deutscb.  Hot.  Geseiis.  13  ;  13.   1895. 

A  fuller  bibiiof^raphy  and  references  may  be  found  in   i'retjakow. 


KXFLANATION    OF    FLATK    X\I. 

Figures  all  drawn  with  camera  lucida,  and  the  original  drawings  reduced 
one-half. 

In  all  of  the  figures,  e.s.  —  embryo  sac  ;  n.  ■=  nucellus  ;  in.  —  the  integ- 
uments collectively  ;  /'.  /.  —  imier  integument  ;  m.  --  inicropyle  or  niicro- 
pylar  opening  through  the  nucellus  ;  /.  —  pollen  tube  ;  Pr.  proto|>lasm  of 
endiryo  sac. 

Figs.  i.  2,  3,  4,  5,  each  showing  the  embryos  from  a  single  seed,  nat- 
ural size. 

Fui.  6.  Median  section  through  an  ovule  of  Opuntia  vult^niris,  some- 
what diagrammatized,  six  times  natural  size:/-  funiculus;  a  —  attach- 
ment of  funiculus  to  ovule  ;  .r  =  portion  of  nucellus  not  absorbed  when 
seed  is  ripe. 

Fig.  7.  Embryo  sac  showing  three  embryos,  one  from  the  micropylar  end 
and  two  from  the  wall.   X  18. 

F'iG.  8.  Embryo  sac  showing  one  large  embryo  on  the  wall  and  several 
smaller  from  the  micropylar  end.  X  18.  Not  a  section,  but  a  half  seed  laid 
open. 


028 


BOTANICAL  GAZETTE 


[aprm. 


Fig.  9.  Embryo  sac  showing  a  single  embryo  from  the  micropylar  end. 
X  35- 

Fio.  10.  Embryo  sac  showing  embryos  on  the  wall  together  with  the 
branching  mass  from  the  micropylar  end.  Nucellar  cells  drawn  nearly 
exactly  ;  those  of  embryos  exact  on  the  outside  but  only  approximate  in  the 
interior.   X  go. 

Fig.  II.  An  embryo  on  the  wall;  to  show  the  connection  of  cells  of 
embryo  to  those  of  nucellus  ;  a  microtome  section.   X  90. 

Fig.  12.  Beginning  of  budding  from  nucellus  cells  near  the  micropyle. 
X  90. 

Fig.  13.  Cells  of  nucellus  beginning  to  grow  out  at  x  into  an  embryo. 
X  90. 

Fig.  14.  Embryonic  mass  separating  from  the  nucellus.  The  section  is 
cut  diagonally  through  the  apex  of  the  embryo  sac.   X  90. 

Fig.  1 5.  a,  b.  Two  sections  from  one  embryo  sac  to  show  that  some 
apparently  wall-embryos  are  really  from  the  micropylar  mass.   X  i8. 


BOTANICAL  GAZETTE,  XXV. 


PLATE  XVL 


M 


GAXONG  on  POLYKMHRYOXV. 


